Polyester/polyamide blend having improved flavor retaining property and clarity

ABSTRACT

This invention relates to a polyester/polyamide blend having an excellent gas barrier property. More particularly, the present invention relates to combinations of a polyethylene terephthalate polymer and a polyamide polymer having an excellent gas barrier property and short oxygen scavenging induction periods, where the polyamide polymer has a C:A terminal group concentration ratio of 2:1 or more and a C+A terminal group concentration of at least 0.17 meq/g of polyamide polymer, wherein C represents a cumulative total of a terminal carboxyl group concentration and a terminal hydrocarbyl group concentration expressed in meq/g of polyamide, and A represents a terminal amine group concentration expressed in meq/g of polyamide.

1. FIELD O)F THE INVENTION

This invention relates to polyester/polyamide blends having good gasbarrier properties. More particularly, the present invention relates toblends of transition metal salts, oxygen scavenging polyamide polymers,and polyester polymers having passive carbon dioxide barrier propertiesand controlled induction periods for lengthy active oxygen scavengingactivity.

2. BACKGROUND OF THE INVENTION

Packaging for food, beverages, cosmetics, medicines, and the likerequire high barrier properties to oxygen and carbon dioxide to preservethe freshness of the package contents. Blends containing small amountsof high barrier polyamides, such as poly(m-xylylene adipamide),typically known commercially as MXD-6, with polyesters such aspoly(ethylene terephthalate), PET, enhance the passive barrierproperties of PET.

To further reduce the entry of oxygen into the contents of the package,small amounts of transition metal salts, such as cobalt salts, can beadded to the blend of PET and polyamide to catalyze and actively promotethe oxidation of the polyamide polymer, thereby further enhancing theoxygen barrier characteristics of the package. The active oxygenscavenging of many blends of oxygen scavenging transition metals andpredominantly amine-terminated, low molecular weight polyamides with PETdoes not begin immediately to a significant extent. On the other hand,active oxygen scavenging of comparable compositions containing oxygenscavenging transition metal/high molecular weight commercial grade MXD-6blends begins almost immediately, within a few days. The inductionperiod (the period of time from the formation of the article until thetime the oxygen transmission rate is significantly reduced) of many lowmolecular weight, amine-terminated polyamide/cobalt salt blends in PETextends well into the life cycle of a filled package so as to make theseblends practically useless as active oxygen scavengers. In some cases,the induction period is so long that no significant oxygen scavengingtakes place before the contents of the package are consumed, such thatit no longer makes practical sense to refer to an induction period.

In addition to reducing the induction period relative to oxygenscavenging transition metal/predominantly amine-terminated low molecularweight polyamide blends in PET, it would also be yet more desirable tocontrol the induction period. The complete elimination of an inductionperiod is not the most preferred means for reducing the inductionperiod. It would be more desirable to have an induction period of somelength of time in order to extend the useful life of oxygen scavengingby the action of the oxygen scavenging transition metal and oxygenscavenger, referred to as the capacity to scavenge oxygen. Containersare usually stored in inventory for a period of time, open to air bothinside and out of the container, before they are filled with theirdesignated contents. During the period of storage, oxygen scavenging isnot necessary. If the compositions exhibit a very short inductionperiod, oxygen scavenging begins during the period of time when thecontainers are not filled, with the drawback that the useful scavengingcapacity is reduced.

Accordingly, it would be desirable to control the induction period andcommence the active oxygen scavenging at about the time the container isfilled, typically 2-4 weeks after the article is formed, while providinga shorter induction period than in oxygen scavenging transitionmetal/low molecular weight amine-terminated polyamide blends in PET.

3. SUMMARY OF THE INVENTION

There is now provided a polyester polymer composition having passivebarrier and active oxygen scavenging properties in which the inductionperiod of the active oxygen scavenging system is shortened. In anotherembodiment, there is provided a polyester composition having passivebarrier properties and active oxygen scavenging properties in which theinduction period is controlled to have a measure of delay before activeoxygen scavenging commences, yet the delay is shorter relative to lowmolecular weight, amine terminated polyamide/Co blends. There is alsoprovided a polyester polymer composition having high active scavengingproperties over a continuous lengthy period of time. The polyesterpolymer composition comprises:

(A) a polyester polymer comprising:

-   -   (i) a polycarboxylic acid component comprising at least 60 mole        % of the residues of terephthalic acid, derivates of        terephthalic acid, naphthalene-2,6-dicarboxylic acid,        derivatives of naphthalene-2,6-dicarboxylic acid, or mixtures        thereof, and    -   (ii) a polyhydroxyl component comprising at least 30 mole % of        the residues of C₂-C₄ aliphatic saturated diols,        based on 100 mole percent of the polycarboxylic acid residues        and 100 mole percent polyhydroxyl residues, respectively, in the        polyester polymer; and

(B) a polyamide polymer in an amount ranging from 0.10% wt. % to 10.0wt. %, based on the weight of (A) and (B), having a C:A terminal groupconcentration ratio of 2:1 or more and a C+A terminal groupconcentration of at least 0.17 meq/g of polyamide polymer, wherein Crepresents a cumulative total of a terminal carboxyl group concentrationand a terminal hydrocarbyl group concentration expressed in meq/g ofpolyamide, and A represents a terminal amine group concentrationexpressed in meq/g of polyamide; and

(C) an oxygen scavenging transition metal catalyst. There is alsoprovided a concentrate comprising:

(A) a polyester polymer comprising:

-   -   (i) a polycarboxylic acid component comprising at least 60 mole%        of the residues of terephthalic acid, derivates of terephthalic        acid, naphthalene-2,6-dicarboxylic acid, derivatives of        naphthalene-2,6-dicarboxylic acid, or mixtures thereof, and    -   (ii) a polyhydroxyl component comprising at least 30 mole % of        the residues of C₂-C₄ aliphatic saturated diols,        based on 100 mole percent of the polycarboxylic acid residues        and 100 mole percent polyhydroxyl residues in the polyester        polymer; and

(B) a polyamide polymer in an amount ranging from 10% wt. % to 50.0 wt.%, based on the weight of (A) and (B), having a C:A terminal groupconcentration ratio of 2:1 or more and a C+A terminal groupconcentration of at least 0.17 meq/g of polyamide polymer, wherein Crepresents a cumulative total of a terminal carboxyl group concentrationand a terminal hydrocarbyl group concentration expressed in meq/g ofpolyamide, and A represents a terminal amine group concentrationexpressed in meq/g of polyamide.

4. DETAILED DESCRIPTION OF THE INVENTION

The present invention may be understood more readily by reference to thefollowing detailed description of the invention and the examplesprovided therein.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. For example,reference to processing or making a “polymer,” “preform,” “article,”“container,” or “bottle” is intended to include the processing or makingof a plurality of polymers, preforms, articles, containers or bottles.References to a composition containing “an” ingredient or “a” polymer isintended to include other ingredients or other polymers, respectively,in addition to the one named.

By “comprising” or “containing” is meant that at least the namedcompound, element, particle, or method step etc must be present in thecomposition or article or method, but does not exclude the presence ofother compounds, catalysts, materials, particles, method steps, etc,even if the other such compounds, material, particles, method steps etchave the same function as what is named, unless expressly excluded inthe claims.

It is also to be understood that the mention of one or more method stepsdoes not preclude the presence of additional method steps before orafter the combined recited steps or intervening method steps betweenthose steps expressly identified. Moreover, the lettering of processsteps or ingredients is a convenient means for identifying discreteactivities or ingredients and the recited lettering can be arranged inany sequence.

A range of numbers includes and expresses all integers and fractionsthereof between the stated range. A range of numbers expressly includesnumbers less than the stated endpoints and in-between the stated range.

The polyester polymer composition comprises the product produced by theaddition of at least the stated ingredients. Included within thecomposition are blends in which the ingredients can be discretelyidentified such as might occur when none of the ingredients react witheach other or do react with each other but the reaction does not obscureidentification of the ingredients. Also included within the compositionare reaction products made by combining the ingredients in which theform of the ingredients have been modified as by way of known or unknownreactions occurring among the ingredients once combined or thereafterand it is no longer possible to detect the presence of one or moreindividual ingredients.

The intrinsic viscosity values described throughout this description areset forth in dL/g units as calculated from the inherent viscositymeasured at 25° C. in 60/40 wt/wt phenol/tetrachloroethane.

The polyester polymers of the invention are thermoplastic. The form ofthe polyester polymer composition is not limited and can include acomposition in the melt phase polymerization, as an amorphous pellet, asa solid stated polymer, as a semi-crystalline particle, as a compositionof matter in a melt extrusion zone, as a bottle preform, or in the formof a stretch blow molded or extrusion blow molded bottle or otherarticle. The form of the polyester polymer particles is not critical,and such particles are typically formed in the shape of chips, pellets,and flakes.

The measurements of b* color values are conducted according to thefollowing methods. The instrument used for measuring b* color shouldhave the capabilities of a HunterLab UltraScan XE, model U3350, usingthe CIELab Scale(L*, a*, b*), D65 (ASTM) illuminant, 10° observer,integrating sphere geometry. Sample clarity will dictate which mode isused to test the sample (reflectance or transmission). Pellets aretested under ASTM D 6290 “Standard Test Method for Color Determinationof Plastic Pellets” in the reflectance mode. Clear plaques, films,preforms, bottles, and liquids are tested in the transmission mode underASTM D1746 “Standard Test Method for Transparency of Plastic Sheeting.”The instrument for measuring color is set up under ASTM E1164 “StandardPractice for Obtaining Spectrophotometric Data for Object-ColorEvaluation.” Color is determined on a sample by using its absolutevalue—the value determined by the instrument.

More particularly, the following test methods can be used, dependingupon whether the sample is a ground powder, a preform, or a bottle.Color measurements should be performed using a HunterLab UltraScan XE(Hunter Associates Laboratory, Inc., Reston Va.), which employsdiffuse/8° (illumination/view angle) sphere optical geometry, orequivalent equipment with these same basic capabilities. The color scaleemployed is the CIE L*a*b* scale with D65 illuminant and 10° observerspecified. Pellets are measured in RSIN reflection, specular componentincluded mode according to ASTM D6290, “Standard Test Method for ColorDetermination of Plastic Pellets”. Pellets are placed in a 33-mm pathlength optical glass cell, available from HunterLab, and allowed tosettle by vibrating the sample cell using a laboratory Mini-Vortexer(VWR International, West Chester, Pa.).

Preforms having a mean outer diameter of 0.878 inches and a wallthickness of 144 mils, and bottle sidewall sections having a wallthickness of 11.5 to 12 mils are measured in regular transmission modeusing ASTM D1746, “Standard Test Method for Transparency of PlasticSheeting”. Preforms are held in place in the instrument using a preformholder, available from HunterLab, and triplicate measurements areaveraged, whereby the sample is rotated 90° about its center axisbetween each measurement. Bottle sidewalls are cut from the bottle andheld in place in the instrument using a transmission clamp accessory,available from HunterLab, and duplicate measurements are averaged,whereby each side of the sidewall alternately contacts the sample port.

L*, a*, and b* values measured in transmission mode are somewhatdependent on the sample thickness. Since at one thickness the measuredb* has one value and at another thickness the same polyester polymercomposition can have a different value, the b* values claimed inpreferred embodiments of the invention can be normalized to a thicknessof 12 mils±0.5 mils for bottle sidewalls and two 144 mil sections forpreforms for a wide variety of different perform and bottle sidewallthicknesses by the following equation: T_(h) = T_(o)10^(−β  h)$\beta = \frac{\log_{10}\left( \frac{T_{o}}{T_{d}} \right)}{d}$where

-   -   T_(h)=transmittance at target thickness    -   T_(o)=transmittance without absorption    -   β=Absorption coefficient    -   T_(d)=transmittance measured for sample    -   h=target thickness    -   d=thickness of sample        wherein the target thickness is 11.5 mils for bottle sidewall        (actual thicknesses between 11.5 mils and 12 mils are        acceptable) and for preforms the target thickness is a        combination of two (2) preform walls each with a target        thickness of 144 mils.

The transmittance values are those measured as a function of wavelengthin the visible spectrum and integrated according to ASTM E308, “Practicefor Computing the Color of Objects by Using the CIE System” in thecalculation of the CIE tristimulus values. These calculations, ifdesired, can be performed in the HunterLab Universal software as part ofCMR 2669, available from HunterLab.

We have found that when using low molecular weight amine-terminatedpolyamides in combination with a cobalt salt acting as an oxidationcatalyst blended into polyethylene terephthalate (“PET”) polymers, theinduction period is rather long. The induction period is determinedrelative to an identical control except without the presence of anactive transmission metal catalyst. Once the control and sample oxygentransmission rates are measured, the induction period of a samplebecomes the point in time when the oxygen transmission rate (“OTR”) ofthe sample is reduced by 50% relative to the pseudo steady state oxygentransmission rate of the control. The OTR is tested according to themethod described below at 23° C., with 50% relative humidity (RH)external to the package, and about 80% RH internal and expressed in theunit of cc STP/day, where cc STP is the number of cubic centimeters thatthe transmitted oxygen would occupy at STP (273 K and 1 atm).

The induction period of blends with a low molecular weight amineterminated polyamide can be rather long, even at optimum catalyst andpolyamide concentrations of 100-150 ppm cobalt and about 3 wt. %polyamide, respectively. However, blends containing polyethyleneterephthalate or polyethylene naphthalate, an oxidation catalyst, andpolyamides prepared in such a way as to have a C:A terminal groupconcentration ratio of 2:1 or more and a C+A terminal groupconcentration of at least 0.17 meq/g of polyamide polymer, producepolymer compositions exhibiting a much shorter induction period toactivate the oxygen scavenging reaction than the same blend using lowmolecular weight polyamides having a predominantly amine end groups. Theinduction period can be shortened to about ½ or ⅓ or less of thatrealized when using the low molecular weight amino terminated versionhaving a C:A ratio of less than 2:1. Not only can the induction periodbe significantly reduced, but we have found that the induction periodcan also be controlled or delayed as desired by adjusting the ratio ofamine residue end groups to the non-amine residue end groups on thepolyamide polymer, as well as the total end group concentration of C+A.Thus, a container can be prepared with immediate passive barrierproperties and active oxygen barrier activity after a desired number ofdays by controlling the end-group types, total number of end groups, andconcentrations of the polyamide. A further un-expected advantage wasobserved by employing the blends of the invention in that the b* colorcharacteristics of the polymers are not sacrificed, and indeed in manyinstances are improved, in preforms used to make bottles by the use ofthe polyester polymer compositions of the invention. Thus, containerswith lower b* color and high barrier to oxygen can be produced withcontrolled active oxygen scavenging induction periods for practicalapplications in packages for beverages, food, cosmetics, personal careproducts, pharmaceuticals, and the like.

Component (A) of the polyester polymer composition is at least apolyester polymer comprising:

-   -   (i) a polycarboxylic acid component comprising at least 60 mole        % of the residues of terephthalic acid, derivates of        terephthalic acid, naphthalene-2,6-dicarboxylic acid,        derivatives of naphthalene-2,6-dicarboxylic acid, or mixtures        thereof, and    -   (ii) a polyhydroxyl component comprising at least 30 mole % of        the residues of C₂-C₄ aliphatic saturated diols,        based on 100 mole percent of the polycarboxylic acid residues        and 100 mole percent polyhydroxyl residues in the polyester        polymer

The reaction of a polycarboxylic acid compound with a polyhydroxylcompound during the preparation of the polyester polymer is notrestricted to the stated mole % ratios since one may utilize a largeexcess of poly-ol if desired, e.g. on the order of up to 200 mole %relative to the 100 mole % of polycarboxylic acid used. The polyesterpolymer made by the reaction does, however, contain the stated amountsof aromatic dicarboxylic acid residues and a C₂-C₄ aliphatic saturateddiol residue.

Derivates of terephthalic acid and naphthalane dicarboxylic acid includeC₁-C₄ dialkylterephthalates and C₁-C₄ dialkyinaphthalates, such asdimethylterephthalate and dimethyinaphthalate

Examples of suitable polyester polymers include polyethyleneterephthalate homopolymers and copolymers modified with one or morepolycarboxylic acid modifiers in a cumulative amount of less than 15mole %, or 10 mole % or less, or 8 mole % or less, or one or morepolyhydroxyl compound modifiers in an amount of less than 70 mole %, or50 mole % or less, or 15 mole % or less, or 10 mole % or less, or 8 mole% or less (collectively referred to for brevity as “PET”) andpolyethylene naphthalate homopolymers and copolymers modified with acumulative amount of with less than 15 mole %, or 10 mole % or less, or8 mole % or less, of one or more polycarboxylic acid modifiers ormodified less than 70 mole %, or less than 50 mole %, or 15 mole % orless, or 10 mole % or less, or 8 mole % or less of one or morepolyhydroxyl compound modifiers (collectively referred to herein as“PEN”), and blends of PET and PEN. A modifier polycarboxylic acidcompound or polyhydroxyl compound is a compound other than the compoundcontained in an amount of at least 60 mole %. The preferred polyesterpolymer is polyalkylene terephthalate, and most preferred is PET.

Preferably, the polyester polymer contains at least 90 mole % ethyleneterephthalate repeat units, and most preferably at least 92 mole %,based on the moles of all repeat units in the polyester polymers.

In addition to a diacid component of terephthalic acid, derivates ofterephthalic acid, naphthalene-2,6-dicarboxylic acid, derivatives ofnaphthalene-2,6-dicarboxylic acid, or mixtures thereof, thepolycarboxylic acid component(s) of the present polyester may includeone or more additional modifier polycarboxylic acids. Such additionalmodifier polycarboxylic acids include aromatic dicarboxylic acidspreferably having 8 to 14 carbon atoms, aliphatic dicarboxylic acidspreferably having 4 to 12 carbon atoms, or cycloaliphatic dicarboxylicacids preferably having 8 to 12 carbon atoms. Examples of modifierdicarboxylic acids useful as an acid component(s) are phthalic acid,isophthalic acid, naphthalene 2,6 dicarboxylic acid if terephthalic acidis present in an amount of at least 60 mole %, terephthalic acid ifnaphthalene 2,6 dicarboxylic acid is present in an amount of at least 60mole %, cyclohexanedicarboxylic acid, cyclohexanediacetic acid,diphenyl-4,4′-dicarboxylic acid, succinic acid, glutaric acid, adipicacid, azelaic acid, sebacic acid, and the like, with isophthalic acid,naphthalene 2,6 dicarboxylic acid, and cyclohexanedicarboxylic acidbeing most preferable. It should be understood that use of thecorresponding acid anhydrides, esters, and acid chlorides of these acidsis included in the term “polycarboxylic acid”. It is also possible fortrifunctional and higher order polycarboxylic acids to modify thepolyester.

Examples of C₂-C₄ aliphatic saturated diols include ethylene glycol,propane diol, and butane diol, among which ethylene glycol is mostpreferred for container applications. In addition to these diols, othermodifier polyhydroxyl compound component(s) may include diols such ascycloaliphatic diols preferably having 6 to 20 carbon atoms and/oraliphatic diols preferably having 3 to 20 carbon atoms. Examples of suchdiols include diethylene glycol; triethylene glycol;1,4-cyclohexanedimethanol; propane-1,3-diol and butane-1,4-diol (whichare considered modifier diols if ethylene glycol residues are present inthe polymer in an amount of at least 60 mole % based on the moles of allpolyhydroxyl compound residues); pentane-1,5-diol; hexane-1,6-diol;3-methylpentanediol-(2,4); neopentyl glycol; 2-methylpentanediol-(1,4);2,2,4-trimethylpentane-diol-(1,3); 2,5-ethylhexanediol-(1,3);2,2-diethyl propane-diol-(1,3); hexanediol-(1,3);1,4-di-(hydroxyethoxy)-benzene; 2,2-bis-(4-hydroxycyclohexyl)-propane;2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane;2,2-bis-(3-hydroxyethoxyphenyl)-propane; and2,2-bis-(4-hydroxypropoxyphenyl)-propane. Typically, polyesters such aspolyethylene terephthalate are made by reacting a glycol with adicarboxylic acid as the free acid or its dimethyl ester to produce anester monomer and/or oligomers, which are then polycondensed to producethe polyester.

Preferred modifiers include isophthalic acid, naphthalene dicarboxylicacid, trimellitic anhydride, pyromellitic dianhydride, 1,4-cyclohexanedimethanol, and diethylene glycol

The amount of the polyester polymer in the polyester polymer compositionranges from greater than 50.0 wt. %, or from 80.0 wt. %, or from 90.0wt. %, or from 95.0 wt. %, or from 97.0 wt. %, or from 99.00 wt. %, andup to about 99.50 wt. % based on the combined weight of all polyesterpolymers and all polyamide polymers. The polyester polymer compositionsmay also include blends of polyester polymer compositions with otherthermoplastic polymers such as polycarbonate. It is preferred that thepolyester composition should comprise a majority of the polyesterpolymer composition of the inventions, more preferably in an amount ofat least 80 wt. %, or at least 95 wt. %, and most preferably 100 wt. %,based on the weight of all thermoplastic polymers (excluding fillers,inorganic compounds or particles, fibers, impact modifiers, or otherpolymers which may form a discontinuous phase). While in mostapplications, the polyester polymer composition does not contain anyfillers, fibers, impact modifiers, or other polymers which form adiscontinuous phase, in an amount of over 5 wt. % based on the weight ofthe whole composition, some applications, such as ovenable food trays,may contain a greater amount of impact modifiers or other fillersbecause of cold storage.

The polyester compositions can be prepared by polymerization proceduresknown in the art sufficient to effect esterification andpolycondensation. Polyester melt phase manufacturing processes includedirect condensation of a dicarboxylic acid with the diol, optionally inthe presence of esterification catalysts, in the esterification zone,followed by polycondensation in the prepolymer and finishing zones inthe presence of a polycondensation catalyst; or ester exchange usuallyin the presence of a transesterification catalyst in the ester exchangezone, followed by prepolymerization and finishing in the presence of apolycondensation catalyst, and each may optionally be solid statedaccording to known methods.

The It.V. of polyester polymer ranges from about at least 0.55, or atleast 0.65, or at least 0.70, or at least 0.75, and up to about 1.15dL/g. The molten polymer from the melt phase polymerization may beallowed to solidify and/or obtain any degree of crystallinity from themelt. Alternatively, the molten polymer can be first solidified and thencrystallized from the glass Component (B) of the polyester compositionis a polyamide polymer having a C:A terminal group concentration ratioof 2:1 or more and a C+A terminal group concentration of at least 0.17meq/g (milliequivalents per gram) of polyamide polymer, wherein Crepresents a cumulative total of a terminal carboxyl group concentrationand a terminal hydrocarbyl group concentration expressed in meq/g ofpolyamide, and A represents a terminal amine group concentrationexpressed in meq/g of polyamide. By a cumulative total within C is meantthat all the terminal end groups selected from carboxylic acids endgroups and hydrocarbyl end groups are added, and allows for the presenceof only carboxylic acid groups, only hydrocarbyl groups, or acombination of both carboxylic acid and hydrocarbyl end groups. Theterminal hydrocarbyl group contains only carbon, hydrogen, andoptionally oxygen atoms as components of the end group. An end group isthe portion of the molecule past the last amide linkage.

The polyamide polymer is preferably present as a physical blend with thepolyester polymer component (A). A variety of methods exist to detectphysical blend, and the method selection is not limited. For example, apolyamide can phase separate using conventional separation techniquessuch as solvent extraction, where at least one of the phases containsthe polyamide polymer essentially distinct from another phase containinga polyester polymer component (A).

The amount of polyamide used in the polyester composition will dependupon the requirements of a particular application. In choosing theamount of desired polyamide, consideration is given for factors such ascolor, the effective reduction in oxygen transmission, and costs, whichare each impacted by the amount of polyamide used.

In general, suitable amounts of polyamide, based on the weight of thepolyester (A) and the polyamide (B), range from greater than 0.5 wt. %,or greater than 1.0 wt. % and up to about 50 wt. % or less, or 20 wt. %or less, or 10 wt. % or less, or 8 wt. % or less, or 6 wt. % or less, or3 wt. % or less, based on the weight of (A) and (B). For preform andbottle applications, suitable amounts of polyamide polymers in apolyester container, based on the weight of polyester (A) and polyamide(B), range from 0.50 wt. %, to 10 wt. %, or preferably from 1.0 to 6 wt.%.

If one desires, a concentrate of the polyester composition of theinvention can be made and let down into an extruder, such as aninjection molding machine, at a desired rate to yield a polyestercomposition containing the final desired amount of polyamide compound inthe finished product, such as a blown bottle. The concentrate contains aconcentration of polyamide polymer which is higher than theconcentration of polyamide polymer in a container. In this way, aconverter retains the flexibility to decide the level of polyamide inthe finished product. Thus, there is also provided a concentratecontaining the polyester polymer (A), and a polyamide compound (B) in anamount ranging from 10.0 wt%, or at least 15.0 wt. %, or at least 20 wt.%, and up to about 50 wt. %, based on the weight of components (A) and(B).

The method for incorporating the polyamide compound into the finishedarticle is not limited. The polyester/polyamide blends of the presentinvention involve preparing the polyester and polyamide by knownprocesses. The polyester and polyamide are separately or in combinationdried in an atmosphere of dried air or dried nitrogen, or under reducedpressure. The polyester and polyamide are mixed. In one method ofincorporation, the polyester and polyamide are melt compounded, forexample, in a single or twin screw extruder. After completion of themelt compounding, the extrudate is withdrawn in strand form, andrecovered according to the usual way such as cutting. Instead of meltcompounding, the polyester and polyamide may be dry-blended andheat-molded or draw-formed into plastic articles.

Alternatively, the polyamide polymer can be added to the melt phasepolymerization for making the polyester polymer, preferably in the latestages of polyester manufacture. In the interest of avoiding or limitingthe number of reactions which contribute to the formation of colorbodies or which may result in the degradation of the polyamide polymer,one may add the polyamide polymer toward the end of the melt phasereaction process, such as in the finisher, toward the end of thefinishing reaction, or even after melt phase production is complete andprior to allowing the molten product to enter the die for makingpellets. The polyamide may also be added as part of a polyolefin basednucleator concentrate where clarity is not critical such as incrystallized thermoformed articles.

Any one of the following methods for making the polyester composition ofthe invention, including concentrates, can be employed:

(i) the polyamide can be added during melt phase manufacture of thepolyester polymer such that the product withdrawn from the melt phasepolycondensation reactor made into a pellet contains the polyamidepolymer; or

(ii) an amorphous polyester pellet can be melt blended with a polyamidepolymer and, after optional crystallization and solid stating, offeredas a finally formulated pellet containing the same concentration ofpolyamide polymer as present in the finished product such that aconverter need only feed the finally formulated pellets through anextruder without a step of separately metering a polyamide stream;

(iii) same as method (ii), except that the amorphous polyester pelletsare first solid stated after which they are melt blended with thepolyamide in an extruder to make pellets, the pellets which are laterfed through an extruder by a converter to make articles; or

(iv) a concentrate can be made by the method of (ii) or (iii) to allow aconverter/compounder to meter and let down the concentrate into thepolyester stream of pellets fed to an extruder for making articles at arate corresponding to the final desired concentration of polyamide inthe article;

or

(v) a salt and pepper blend of polyamide pellets and polyester pellets,one or both optionally ground, can be prepared and then fed as a pelletblend to an extruder such as an injection molding machine.

In each case, the polyamide polymer can be added to the polyesterpolymer as a neat stream of polyamide polymer, in a suitable liquidcarrier, or melt blended with a polyester to provide a solidconcentrate. The number average molecular weight of the polyamidepolymer is not particularly limited to effectuate a measure of oxygenscavenging, provided that the relationship of C+A is 0.17 meq/g ofpolyamide polymer or more. The Mn is desirably above 1000, or above3000. Higher or lower molecular weight polyamide polymers are suitable,such as polyamide polymers having a molecular weight of up to about15,000, or up to 11,500, or 10,000 or less, and even 7500 or less.

Independent of the aforementioned molecular weights, in anotheralternative embodiment, the particular polyamide polymer used has amolecular weight below a film forming molecular weight. Thecharacteristics of a polyamide polymer having a molecular weight at orabove a film forming molecular weight is that a 0.1 mm thick casting ofthe polymer will bend 180° on itself without cracking, is selfsupporting, and can be taken up on a roll while maintaining itsmechanical integrity. 0.1 mm thick polyamide polymer castings having anumber average molecular weight below a film forming molecular weightwill not bend 180° on itself without cracking or forming a permanentcrease.

The end-groups of the polyamide polymer comprise carboxylic acid groupsand/or hydrocarbyl groups, and some primary amine groups. The C:A endgroup concentration ratio is 2:1 or more, wherein C represents thecumulative total of a carboxylic acid residue end group concentrationand a hydrocarbyl residue end group concentration, and A represents anamine residue end group concentration. Suitable ratios include 4:1 ormore, or 10:1 or more, or 30:1 or more, or 50:1 or more, or 100:1 ormore, or 200:1 or more. All else being equal, the particular ratiochosen depends on how long the induction period should last, with thelower ratios extending the induction period and the higher ratiosshortening the induction period. The length of the induction period canbe set as desired.

The polyamide polymer also has a C+A terminal group concentration of atleast 0.17 meq/g of polyamide polymer. Since it is desired to have aperiod of time lapse between the manufacture of the article and theonset of significant oxygen scavenging, the polyamide polymer shouldhave a total end group concentration, counting up all the C groups andthe A groups, of at least 0.17 meq/g. It is believed that the inductionperiod is too short, on the order of less than a few days, when thetotal number of terminal end groups falls below 0.17, especially at highC:A ratios and at higher levels of polyamide polymer. By retaining thetotal number of terminal end groups C+A at 0.17 meq/g or more, even atlower C:A ratios, an induction period can be provided. One may set theC:A ratio to correspond with an induction period tailing off andsignificant active oxygen scavenging commencing at about the time thecontainer is filled with the consumable contents or shortly thereafter.For example, significant active oxygen scavenging can commence 35 daysafter the container is made, or within 1 week before filling the packageup to about 2 weeks after filling the package. This may be accomplishedby experimentally determining the appropriate C:A ratio for a givenpolyamide in the polyester resin into which the polyamide is added whileensuring that the total C+A content remains above 0.17 meq/g. In thisembodiment, significant oxygen scavenging is attained when the oxygentransmission rate falls below 0.020 cc STP/day from the time the bottleis blow molded.

The polyamide polymer component (B) is made by reacting a polycarboxylicacid compound and either a polyamine compound, an amine functionalizedpolyalklydiene, or an amine functionalized polyoxyalkylene polyether, ormade by any other known methods, such as through lactams, using aminoacids, or acid chloride reaction products with diamines. The polyamidepolymer desirably contains an active methylene hydrogen such as benzylichydrogens, allylic hydrogens, or oxyalkylene hydrogens, to ensureeffective and optimal oxygen scavenging activity.

In one embodiment, the polyamide polymer is a reaction productcontaining moieties, preferably in an amount of at least 40 mole %, orat least 70 mole %, or at least 80 mole %, represented by the generalformula:

and the number of such moieties present in the polymer ranges from 1 to200, or from 50 to 150. Preferably, at least 10 wt % of the monomersused to prepare the polyamide contain active methylene groups, such asan allylic group, an oxyalkylene hydrogen, or more preferably at least50% of the repeat units in the polymer contain a benzylic hydrogengroup.

Examples of acids used to make the polyamide include polycarboxylic acidcompounds, amino acids, and chlorides, derivates or anhydrides thereof,including lactams, having from 4 to 50 carbon atoms, or an average of 4to 24 carbon atoms, or an average of 4 to 12 carbon atoms. Examples ofamines used to make the polyamide polymer include polyamines, aminoacids, and the derivatives and anhydrides thereof, including lactams,having from to 50 carbon atoms, or from 2 to 22 carbon atoms.

More specific examples of suitable acids include adipic acid,isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid,resorcinol dicarboxylic acid, naphthalene-2,6-dicarboxylic acid,derivates thereof, tartaric acid, citric acid, malic acid, oxalic acid,adipic acid, malonic acid, galactaric acid, 1,2-cyclopentanedicarboxylic acid, maleic acid, fumaric acid, itaconic acid,phenylmalonic acid, hydroxyphtalic acid, dihydroxyfumaric acid,tricarballylic acid, benzene-1,3,5-tricarboxylic acid, 1,2,4-benzenetricarboxylic acid, isocitric acid, mucic acid, glucaric acid, succinicacid, glutaric acid, suberic acid, azelaic acid, sebacic acid,decanedicarboxylic acid, isophthalic acid, pimelic acid, brassylic acid,thapsic acid, glutaconic acid, a-hydromuconic acid, [bgr]-hydromuconicacid, a-butyl-a-ethyl-glutaric acid, diethylsuccinic acid, hemimelliticacid, benzophenone tetracarboxylic dianhydride, chlorendic anhydride,hexahydrophthalic anhydride, tetrahydrophthalic anhydride, trimelliticanhydride, alkanyl succinic anhydride, 5-sodiosulfoisophthalic acid,5-lithiosulfoisophthalic acid, the unsaturated acids and dimerized ortrimerized fatty acids, including those found in natural sources such asBorage Oil, Flaxseed oil, and Primrose oil, lactams such as caprolactam,enantholactam, laurolactam, amino acids such as 6-aminocaproic acid,7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid,12-aminododecanoic acid, and mixtures of two or more thereof.

The dicarboxylic acids may be used either individually or mixed with oneanother. The free dicarboxylic acids may also be replaced by thecorresponding dicarboxylic acid derivatives, for example dicarboxylicacid esters of alcohols having from 1 to 4 carbon atoms or dicarboxylicanhydrides or dicarboxylic acid chlorides.

More examples of polyamines useful in the practice of the invention arethose represented by the formula:H₂N—[—X—NH—]_(n)—H

wherein n is a nominal integer ranging from 1 to 10; and X is a divalent1-500 carbon atom moiety comprised of a saturated or unsaturated,branched or unbranched hydrocarbon radical, one or more aryl or alkarylgroups, or one or more alicyclic groups. X can be a lower alkyleneradical having 1-22, or 2-8, carbon atoms.

Suitable aliphatic polyamines include methylene polyamines, ethylenepolyamines, butylene polyamines, propylene polyamines, pentylenepolyamines, hexylene polyamines, heptylene polyamines, etc. The higherhomologs of such amines and related aminoalkyl-substituted piperazinesare also included. More specific examples include ethylene diamine,di(trimethlyene) triamine, diethylene triamine, di(heptamethylene)triamine, triethylene tetramine, tripropylene triamine, tetraethylenepentamine, pentaethylene hexamine, dipropylene triamine, tributylenetetramine, hexamethylene diamine, dihexamethylene triamine, 1,2-propanediamine, 1,3-propane diamine, 1,2-butane diamine, 1,3-butane diamine,1,4-butane diamine, 1,5- pentane diamine, 1,6-hexane diamine,2-methyl-1,5-pentanediamine, 2,5- dimethyl-2,5-hexanediamine,octamethlyene diamine, pentaethylene diamine, decamethylene diamine, andthe like.

Cycloaliphatic polyamines include isophoronediamine,4,4′-diaminodicyclohexylmethane, menthane diamine,1,2-diaminocyclohexane, 1,4-diaminocyclohexane; and aromatic amines suchas p- and m-xylylenediamine, 4,4′-methylenedianiline,2,4-toluenediamine, 2,6-toluenediamine, polymethylenepolyphenylpolyamine; 1,3-bis(aminomethyl )benzene, 1,3-phenylened iamineand 3,5- diethyl-2,4-toluenediamine.

Hydroxy polyamines, e.g., alkylene polyamines having one or morehydroxyalkyl substituents on the nitrogen atoms, are also useful inpreparing the polyamide polymer of the invention. Examples includehydroxyalkyl-substituted alkylene polyamines in which the hydroxyalkylgroup has less than about 10 carbon atoms. Examples of suchhydroxyalkyl-substituted polyamines includeN-(2-hydroxyethyl)-ethylenediamine,N,N′-bis(2-hydroxyethyl)ethylenediamine, monohydroxypropyl-substituteddiethylene triamine, dihydroxypropyltetraethylenepentamine andN-(3-hydroxybutyl)tetramethylenediamine. Higher homologs obtained bycondensation of the above-illustrated hydroxyalkyl-substituted alkyleneamines through amino radicals or through hydroxy radicals are likewiseuseful.

Suitable aromatic polyamines include p- and m-xylylene diamine,methylene dianiline, 2,4-toluenediamine, 2,6-toluenediamine,polymethylene polyphenylpolyamine, and mixtures thereof. Higherhomologs, obtained by condensing two or more of the above-illustratedalkylene amines, are also useful.

Mixtures of two or more of any of the above mentioned polyamines may beused to react with the polycarboxylic acid. It is to understood thatpractically any polyamine composition used to react with thepolycarboxylic acid will not be 100% pure, and will most likely containreaction by-products with the identified amine being the predominantcompound in the composition. The same can be said for the polycarboxylicacid composition, although a 100% pure composition can be included aswell.

Other groups related to the amide group formed by the reaction betweenthe carboxyl group and the polyamine that are within the meaning of theterm amide include the imides and the amidines.

Most preferably, the polyamide polymer contains active methylene groups,such as may be found on allylic group hydrogen atoms, benzylic grouphydrogens, and alpha oxyalkylene hydrogens. Such hydrogen atoms may beexpressed in the following respective structural moieties as beinglinked to the carbons illustrated in bold:

wherein R is a hydrogen or an alkyl group. These groups may beincorporated into the polyamide using polyamines or polycarboxylic acidcompounds containing one or more of such active methylene groups.

Amine functionalized polyoxyalkylene polyethers can be made byconventional techniques, and are usually the reaction products ofpolyamine compounds with a polyoxyalkylene polyether polyol. Examples ofsuitable polyoxyalkylene polyether polyols are those having a numberaverage molecular weight of 800 to 12,000, they may be block or randomor block/random copolymers, or homopolymers, obtained by polymerizingalkylene oxides with polyhydric alcohols or polyamines as the initiator.Any suitable alkylene oxide may be used such as ethylene oxide,propylene oxide, butylene oxide, amylene oxide, and mixtures of theseoxides. The polyoxyalkylene polyether polyols may be prepared from otherstarting materials such as tetrahydrofuran and alkyleneoxide-tetrahydrofuran mixtures; epihalohydrins such as epichlorohydrin;as well as aralkylene oxides such as styrene oxide.

The alkylene oxides may be added to the initiator, individually,sequentially one after the other to form blocks, or in mixture to form aheteric polyether. The polyalkylene polyether polyols may have eitherprimary or secondary hydroxyl groups. It is preferred to use, as thealkylene oxides, propylene oxide, butylene oxide, or tetrahydrofuran.Preferred polyols also include, however, those containing or terminatedwith ethylene oxide in the amount from 1 to 30 weight percent. Includedamong the polyether polyols are polyoxyethylene glycol, polyoxypropyleneglycol, polyoxybutylene glycol, polytetramethylene glycol; blockcopolymers, for example combinations of polyoxypropylene andpolyoxyethylene, poly-1,2-oxybutylene and polyoxyethylene polyols,poly-1,4-tetramethylene and polyoxyethylene polyols or polyoxypropylenepolyols; and copolymer polyols prepared from blends or sequentialaddition of two or more alkylene oxides. The polyalkylene polyetherpolyols may be prepared by any known process such as, for example, theprocess disclosed by Wurtz in 1859 and Encyclopedia of ChemicalTechnology, Vol. 7, pp. 257-262, published by Interscience Publishers,Inc. (1951) or in U.S. Pat. No. 1,922,459.

Suitable initiator molecules include aniline, N-alkylphenylene-diamines,2,4′-, 2,2′-, and 4,4′- methylenedianiline, 2,6- or 2,4-toluenediamine,vicinal toluenediamines, o-chloro-aniline, p-aminoaniline,1,5-diaminonaphthalene, methylene dianiline, the various condensationproducts of aniline and formaldehyde, and the isomeric diaminotoluenes;and aliphatic amines such as mono-, di, and trialkanolamines, ethylenediamine, propylene diamine, diethylenetriamine, methylamine,triisopropanolamine, 1,3-diaminopropane, 1,3-diaminobutane, and1,4-diaminobutane; trimethylolpropane, glycerine, sucrose, sorbitol,ethylene glycol, propylene glycol, dipropylene glycol, pentaerythritol,and 2,2-bis(4-hydroxyphenyl)-propane.

Suitable polyamine and polycarboxylic acid compounds for functionalizingthe polyoxyalkylene polyether polyols include any of the aforementionedpolyamine or polycarboxylic acid compounds.

Suitable amine and carboxylic acid functionalized polyalkylenedienes areavailable commercially as HYCAR reactive liquid polymers from HanseChemie. Examples of polyalkylenedienes are those obtained bypolymerizing diene compounds, such as 1,4-butadiene; 1,2-butadiene;1,4-isoprene; 3,4-isoprene; 2,3-dimethyl butadiene; chloroprene;2,3-chloroprene; allene; and 1,6-hexatriene.

The polyamides can be obtained by using synthetic procedures that arewell known in the art. Polyamides are generally prepared by melt phasepolymerization from a diacid-diamine complex which may be preparedeither in situ or in a separate step. In either method, the diacid anddiamine (which includes any of the functionalized polyethers andpolyoxyalklyenedienes) are used as starting materials. Alternatively, anester form of the diacid may be used, preferably the dimethyl ester. Ifthe ester is used, the reaction must be carried out at a relatively lowtemperature, generally 80 to 120° C., until the ester is converted to anamide. The mixture is then heated to the polymerization temperature.

Synthetic methods to make a polyamide polymer with carboxylic acidterminal groups include using an excess of the polycarboxylic acidcompound in a reaction between the polyamine compound and thepolycarboxylic acid compound. The molar excess of polycarboxylic acidcan be combined with the polyamine prior to the onset of polymerizationreaction. Alternatively, a carboxylic acid terminated polyamide polymercan be made by reacting together any desired molar ratio ofpolycarboxylic acid compound with a polyamine compound, such as aequimolar ratio or even an excess of the polyamine compound, and uponsubstantial completion of the reaction, adding a polycarboxylic acidcompound to chain terminate the primary amine with carboxylic acid endgroups.

Synthetic methods to make a polyamide polymer end capped with ahydrocarbyl group include, but are not limited to, a two step processcomprising reacting together any desired molar ratio of polycarboxylicacid compound with a polyamine compound, such as a equimolar ratio oreven an excess of the polyamine compound, and upon completing thisreaction to a desired degree, which may be less than completion up tosubstantial completion, then in a second step adding the hydrocarbylcompound having a group reactive with an amine to chain terminate theprimary amine groups with hydrocarbyl end groups. In like manner, astoichiometric excess of the polycarboxylic acid compound may be reactedwith the polyamine compound, followed by adding a hydrocarbyl compoundhaving a group reactive with the carboxylic acid groups to chainterminate the carboxylic acid groups in part or wholly with hydrocarbylgroups.

Alternatively, the polyamine compound, the polycarboxylic acid compound,and the hydrocarbyl compound may be added to a reaction vessel followedby reacting together these reactants randomly in one step instead offollowing a two step process. Alternatively, a polyamide polymercontaining carboxylic acid end groups or hydrocarbyl end groups can bemade by reacting a high molecular polyamide under high shear in anextruder in the presence of a hydrocarbyl capping agent reactive withamine groups to obtain a predominately carboxyl and/or hydrocarbylterminated polyamide polymer.

In any of these synthetic methods, the ingredients can be mixed togetherand reacted. However, in the course of making a carboxylic acidterminated polyamide compound, it is preferable to add a stream ofpolyamine compounds to the complete or substantially complete quantityof the polycarboxylic acid compounds so as to react out the primaryamine functional groups.

These reactions may be carried out in the presence of absence ofsolvents or catalysts. A useful solvent, if used, is simply water.Conventional catalysts may be used to prepare the polyamides of theinvention. Such catalysts are described in Principles of Polymerization”4^(th) ed by George Odian 2004; “Seymour/Carraher's Polymer Chemistry”6^(th) ed rev and expanded 2003; and “Polymer Synthesis: Theory andPractice” 3^(rd) ed by D. Braun 2001.

The polycarboxylic acid and/or hydrocarbyl compounds may be reacted withthe polyamine compound at elevated temperatures, suitably attemperatures ranging from about 120° C. to about 170° C. for a timesufficient to substantially complete the reaction, usually from about 4to about 12 hours. The reaction can be controlled by applying pressure.If the reaction proceeds with some difficulty, vacuum may be appliedduring the course of the reaction or towards the end of the reaction todrive toward completion and further molecular weight build up.

As noted above, hydrocarbyl capping agents can be added during thecourse of polyamide synthesis at any desired stage, such as at reactioninitiation, after half the reaction is completed, or when about 90% ormore of the reaction is complete.

The hydrocarbyl capping agents are those compounds having one functionalgroup capable of reacting with either a primary or secondary amine, orhaving one functional group capable of reacting with a carboxylic acidgroup, and no additional functional groups reactive with a primary orsecondary amine or a carboxylic acid group under the polymerizationconditions actually used. The hydrocarbyl capping agents, upon reactionthrough the functional group, contain carbon, hydrogen, and optionallyoxygen atoms making up the end group.

Examples of hydrocarbyl capping agents include compounds, oligomers, andpolymers having one carboxylic acid group, anhydrides carboxylic acids,one glycidyl group, or one amine group; to which each are linked througha covalent bond a hydrocarbon containing carbon and hydrogen atoms, andoptionally oxygen atoms (e.g. ether linkages, hydroxyl groups).Hydrocarbyl capping agents include monocarboxylic acid compounds, thevarious anhydrides, mono-glycidyl compounds and mono-amine compounds,their oligomers, and their polymers.

Suitable monocarboxylic acid compounds include aliphatic, alicyclic,aryl, or alkaryl acids. The number of carbon atoms is not particularlylimited, and can include those acids having from 1 to 500 carbon atoms,but more typically will have from 1 to 24 carbon atoms. Themonocarboxylic acid may be substituted or unsubstituted, saturated orunsaturated, branched or unbranched.

Examples include the substituted or un-substituted benzoic acids,substituted or un-substituted naphthalenic acids, substituted orun-substituted phenolic acids, acetic acid, formic acid, propionic acid,butyric acid, caproic acid, glycolic acid, lactic acid, mandelic acid,stearic acid, pentanoic acid, 2-chloropropionic acid, 3-chloropropionicacid, 2,2-dichloropropionic acid, hexanoic acid, 2-ethyl-hexanoic acid,cyclohexanecarboxylic acid, dodecanoic acid, palmitic acid, oleic acid,3-mercapto-propionic acid, ricinoleic acid, 4-methylbenzoic acid,salicylic acid anthranilic acid, heptanoic acid, octanoic acid, decanoicacid, undecanoic acid, and octanoic acid.

Also included are aliphatic, branched or unbranched, saturated orunsaturated, mono-carboxylic acid capping polymers having from 25 to 600carbon atoms. Examples of such polymers include the polyoxyalkylenepolyether polymers having a carboxylic acid group. Examples of suitableoxyalkylene groups are those derived from ethylene oxide, propyleneoxide, butylene oxide, or mixtures thereof, in random order or as blockcopolymers.

Examples of monoglycidyl compounds include aliphatic, alicyclic, oraromatic compounds attached to a monoglycidyl functional group. Thesecategories would include the unsaturated epoxy hydrocarbons of butylene,cyclohexene, styrene oxide and the like; epoxy ethers of monovalentalcohols such as methyl, ethyl, butyl, 2-ethylhexyl, dodecyl alcohol andothers; epoxides of the alkylene oxide adducts of alcohols having atleast 8 carbon atoms by the sequential addition of alkylene oxide to thecorresponding alkanol (ROH), epoxy ethers of monovalent phenols such asphenol, cresol, and other phenols substituted in the o- or p-positionswith C (1)-C (21 )branched or unbranched alkyl aralkyl, alkaryl, oralkoxy groups such as nonylphenol; glycidyl esters of mono-carboxylicacids such as the glycidyl ester of caprylic acid, the glycidyl ester ofcapric acid, the glycidyl ester of lauric acid, the glycidyl ester ofstearic acid, the glycidyl ester of arachidic acid and the glycidylesters of alpha, alpha-dialkyl monocarboxylic acids described in U.S.Pat. No. 3,178,454, hereby incorporated by reference; epoxy esters ofunsaturated alcohols or unsaturated carboxylic acids such as theglycidyl ester of neodecanoic acid, epoxidized methyl oleate, epoxidizedn-butyl oleate, epoxidized methyl palmitoleate, epoxidized ethyllinoleate and the like; phenyl glycidyl ether; allyl glycidyl ethers,and acetals of glycidaldehyde.

Specific examples of monoglycidyl compounds include alkyl glycidylethers with 1-18 linear carbon atoms in the alkyl chain such as butylglycidyl ether or a mixture of C8-C14 alkyls, cresyl glycidyl ether,phenyl glycidyl ether, nonylglycidyl ether, p-tert-butylphenylglycidylether, 2-ethylhexyl glycidyl ether, and the glycidyl ester ofneodecanoic acid.

Suitable mono-amine compounds include those having one primary aminegroup and a hydrocarbyl group having from 1-1000 carbon atoms. Examplesinclude 4-phenylbenzyl amine, benzyl amine, butyl amine, sec-butylamine,cyclohexylamine,decylamine, dodecylamine, ethylamine, heptylamine,hexylamine, isopropylamine, p-methoxybenzylamine, 2-methoxyethylamine,methylamine,octadecylamine, octylamine, pentylamine,phenethylaminel-phenylethylamine, propylamine, tetradecylamine,2-aminomethylpyridine, 4-aminomethylpyridine, aminodiphenylmethane,stearyl amine, and polyoxyalkylene monoamines such as those obtainedunder the trademark JEFFAMINE® M series, and salts thereof. Primaryaromatic amines include; aniline,(m,p,o)-anisidine,(m,p,o)-bromoaniline,(m,p,o)-chloroaniline,2,4-dichloroaniline, 2,5-dichloroaniline, 2,5-dimethoxyaniline,2,4-dimetylaniline, 2,5-dimethylaniline, 2,6-dimethylaniline,p-ethylaniline, p-iodoaniline, (m,p,o)-nitroaniline, m-phenoxyaniline,propylaniline, (m,p,o)-toluidine, 2,4,6-tribromoaniline,and2,4,6-trichloroaniline, and salts thereof. Hetrocyclic amines include;2-aminopyridine, 3-aminopyridine, 3-aminoquinoline, 8-aminoquinoline,and salts thereof.

Preferred polyamide polymers are those obtained from a reactantcontaining a benzylic hydrogen, from a viewpoint of their commercialavailability, cost, and performance, preferred polyamides are obtainedfrom a reactant containing a xylylene moiety, or a m-xylylene moiety, ora polymer containing any one of these residues in the polymer chain.More preferred examples include poly(m-xylylene adipamide) modified orunmodified polyamide, and a poly(m-xylylene adipamide-co-isophthalamide)modified or unmodified polyamide, each of which may be chain terminatedwith a hydrocarbyl capping agent such as those listed above, or modifiedwith any other reactant, including those identified above.

Component (C) is a oxygen scavenging transition metal catalyst activefor oxidizing an oxidizable component, such as a polyamide. The catalystmay or may not be consumed in the oxidation reaction, or if consumed,may only be consumed temporarily by converting back to a catalyticallyactive state. As noted in U.S. Pat. No. 5,955,527, incorporated fullyherein by reference, a measure of the catalyst may be lost in sidereactions, or the catalyst may be viewed as an initiator “generatingfree radicals which through branching chain reactions lead to thescavenging of oxygen out of proportion to the quantity of “catalyst”.

Examples include cobalt added in the +2 or +3 oxidation state, rhodiumadded in the +2 oxidation state, and copper added in the +2 oxidationstate. The metals may be added in salt form, most conveniently ascarboxylate salts, such as cobalt octanoate, cobalt acetate, or cobaltneodecanoate.

The amount of catalyst in the polyester composition is effective toactively scavenge oxygen. It is desirable to provide sufficient amountsof oxygen scavenging transition metal catalyst to see significantscavenging effects, and this amount will vary between differenttransition metals and also depend upon the degree of scavenging desiredor needed in the application.

While amounts ranging from about 10 ppm to 1000 ppm are suitable, formost applications, little if any effect is expected to be seen usingamounts toward the lower end of the range between 10 ppm and 30 ppm. Ina preferred embodiment, the amount of oxygen scavenging transition metalcatalyst is at least 50 ppm, or at least 60 ppm, or at least 75 ppm, orat least 100 ppm. Amounts greater than about 400 ppm, while continuingto be effective, are not expected to provide an incremental improvementsufficient to justify added costs. The reported amounts are based on theweight of the polyester polymer composition and measured on the metal,not its compound weight as added to the composition. In the case ofcobalt as the oxygen scavenging transition metal, preferred amounts areat least 50 ppm, or at least 60 ppm, or at least 75 ppm, or at least 100ppm, or at least 125 ppm. The catalyst can be added neat or in a carrier(such as a liquid or wax) to an extruder or other device for making anarticle, or it can be added in a concentrate with a polyamide polymer,in a concentrate with a polyester polymer, or in a concentrate with apolyester/polyamide blend.

The polyester composition of the invention now allows one to not onlydecrease the induction period significantly compared with low molecularweight amine terminated polyamide formulations, and to control theinduction period, but in another embodiment, the oxygen transmissionrate per day can also be significantly reduced. The oxygen transmissionrate per day can be advantageously reduced in the absence ofnanocomposite clays or silicates, thereby reducing resin compositioncosts.

The life of active oxygen scavenging using the composition of theinvention is quite long once significant active oxygen scavenging hascommenced. In the polyester polymer compositions of the invention,active oxygen scavenging can continue for at least 180 days, and even360 days or more, preferably continuously below 0.01 cc STP/day.

In another embodiment, for a continuous period of 50 days measured atany time within a period after the manufacture of a blow moldedpolyester container and before 100 days after its manufacture, theoxygen transmission rate of oxygen through the bottle does not exceed0.020 cc STP/day, preferably does not exceed 0.010 cc STP/day, and evendoes not exceed 0.005 cc STP/day. Preferably, the 50 day continuousperiod begins within 35 days after blow molding the polyester container,or begins within 15 days after making the blow molded container.

In yet another embodiment, there is provided a blow molded polyesterbottle having an oxygen transmission rate of 0.020 cc STP/day or less,more preferably 0.010 cc STP/day or less, for a continuous period of 40days at any time within a period when the bottle is manufactured and 100days thereafter, preferably 80 days thereafter, wherein the bottlecomprises an oxygen scavenging oxygen scavenging transition metal,preferably cobalt, in an amount of 50 ppm to 300 ppm or less, and apolyamide having a C:A ratio of 2:1 or more and a total C+A terminalgroup concentration of at least 0.17 meq/g. Preferably, the 40 dayperiod commences later than 7 days after the bottle is made, and morepreferably begins 10 days after making the container.

The container using the polyamide polymers of the invention are capableof continuously sustaining these low transmission rates even beyond 40or 50 days, such as for a period of 100 days, or 160 days, and even for365 days. Of course, the measurement period would be adjustedaccordingly to accommodate the extended test period. Furthermore, thepolyester polymer compositions are capable of providing a combination ofsustained and continuous periods of low oxygen transmission rates andshort induction periods.

The test conditions for measuring the oxygen transmission rate in thecase of comparing an acid or hydrocarbyl terminated polyamide polymer toa low molecular weight amine terminated polymer are not particularlylimited, since benefits can be seen under a wide range of testconditions relative to the low molecular weight amine terminatedpolyamide compound, provided that the testing conditions are the samewhenever a comparison is made. The test conditions used for measuringthe oxygen transmission rate where relative values are not used, such asin the two embodiments immediately above, are as follows:

The oxygen transmission rate tests were performed using 25 gram, 20ounce stretch blow molded bottles which had a sidewall thickness ofabout 0.011 (plus or minus 0.0015) inches (0.028 cm plus or minus 0.0038cm). The 20 ounce bottles were fitted the day following blow molding foroxygen package transmission testing. Prior to measurement, the bottle issealed by gluing it to a brass plate that is connected to a 4 way valveover the finish. This mounting technique seals the bottle, whileallowing for control of test gas access. The mounting is assembled asfollows. First a brass plate is prepared by drilling two ⅛ inch holesinto the plate. Two lengths of ⅛ soft copper tubing (which will bedesignated A and B) are passed through the holes in the plate and thegaps between the holes and the tubes are sealed with epoxy glue. One endof each of these tubes is attached to the appropriate ports on a 4-wayball valve (such as Whitey model B43YF2). Tubing (which will bedesignated C and D) and connections are also attached to the other portsof the ball valve to allow the finished assembly to be connected to anOxtran oxygen permeability tester (Modern Control, Inc. Minneapolis,Minn.). This mounting is then glued to the finish of the bottle to betested so that tubes A and B extend into the interior of the bottle. Theopen end of one tube is positioned near the top of the package and theopen end of the other is positioned near the bottom to ensure goodcirculation of the test gas within the bottle. Gluing is typicallyperformed in two steps using a quick setting epoxy to make the initialseal and temporarily hold the assembly together and then a secondcoating of a more rugged Metalset epoxy is applied. If desired the brassplate may be sanded before mounting to clean the surface and improveadhesion. If the 4 tubes are correctly connected to the 4-way valve,then when the valve is in the “Bypass” position, tubes A and Bcommunicate and tubes C and D communicate, but tubes A and B do notcommunicate with tubes C and D. Thus the package is sealed. Similarly,when the valve is in its “Insert” position, tubes A and D communicateand tubes B and C communicate, but A and D do not communicate with tubesB and C, except through the interior of the bottle. Thus the bottle canbe swept with purge or test gas.

Once the bottle is mounted on the assembly, it is swept with anoxygen-free gas, and the conditioning period begins. After severalminutes of purging, the 4-way valve is moved to the Bypass position,sealing the bottle. At that point the entire bottle and mountingassembly may be disconnected from the purge gas supply withoutintroducing oxygen into the interior of the bottle. Typically 3 bottlesof each formulation were mounted for testing.

When the oxygen transmission rate of the bottle is to be tested, it isplaced inside an environmental chamber. Under normal operation thesechambers control the external conditions at 23° C. plus or minus 1° C.and 50% relative humidity plus or minus 10%. These chambers containtubing connections to an Oxtran 1050 or Oxtran 1050A instrument and themounting is connected to the Oxtran tester via tubes C and D. Carriergas (nitrogen containing on the order of 1% hydrogen), which ishumidified using a bubbler, is supplied to the instruments and thetubing in the environmental chamber. Both the Oxtran 1050 and 1050A usea coulometric sensor to measure oxygen transmission rates and both havepositions for 10 samples to be mounted on the instrument at one time.Typically, 9 test bottles and 1 control package were run in a set. Oncesamples were mounted in the chamber, the 4-way valve is turned to theInsert position and the system is allowed to recover from theperturbation caused by this process.

After allowing the system to recover, the test is then begun by“inserting” the instrument sensor in-line. The test sequence iscontrolled by a specially written LabView™ software interface for theinstrument. Basically, the instrument automatically advances through thetest cells using a preset interval that allows the instrument tostabilize after each cell change as the test gas from the bottle mountedon the cell is routed through the coulometric sensor, generating acurrent. That current is passed through a resistor, which creates avoltage that is proportional to the oxygen transmission rate of thepackage plus the leak rate of that cell and package assembly. Typicallythe instrument is allowed to index through each of the cells 3 or moretimes and the average of the last 3 measurements is used. Once thesereadings are obtained, the 4-way valves are moved to their Bypasspositions and this process is repeated, providing a measure of the leakrate for the cell and assembly. This value is subtracted from the valueobtained for the package, cell and assembly to yield the value for thepackage. The value is corrected for the average barometric pressure inthe laboratory and reported as the oxygen transmission rate (OTR) of thebottle (in cc(STP)of oxygen/day). At this point the test is terminatedand the bottles are removed from the instrument (with the 4-way valvesstill in the Bypass position).

Between tests, bottles were stored at ambient (RH, lighting, barometricpressure) conditions in a lab (22° C. plus or minus 4° C.) with theinterior isolated from air. After a period of time, the bottle isreconnected to the Oxtran and a new set of transmission measurementscollected. In this manner, it is possible to monitor the behavior of thebottle over several weeks or months.

It was quite surprising to find that the polyamide polymers having a C:Aratio of 2:1 or higher and C+A greater than 0.17 meq/g, in polyesterpolymer compositions containing an oxygen scavenging transition metalcatalyst, had remarkably better oxygen scavenging performance than thesame compositions made with low molecular weight amine terminatedpolyamide polymers under the same test conditions, in the sense that thebottle made with the compositions of the invention exhibitedsignificantly shorter induction times and preferably have lower overalloxygen transmission rates. The examples below illustrate this effect. Ina preferred embodiment, the polyester resin compositions of theinvention are less yellow as measured by bottle sidewall b* color thanthe same formulation made with predominately amine end cappedpolyamides. For example, the polyester resin compositions, such aspreforms, containing a transition metal oxygen scavenging catalyst madewith the predominately acid or hydrocarbyl end capped polyamides exhibita bottle preform b* color of +3.0 or less, or +2.0 or less, or +1.0 orless, and even having a b* in the negative region.

The polymer composition of the invention can be used in multi-layeredlaminate barrier packaging. Such multi-layered packages, however, areexpensive to make. An advantage of the invention is that both passivebarrier to oxygen and active oxygen scavenging can be obtained in onelayer. Accordingly, there is provided a mono-layer bottle comprising(A), (B), and (C) components.

The blends of the invention are useful as the polymer composition usedto make and as found in moldings of all types by extrusion or injectionmolding, and for making thermoformed articles.

Specific applications include containers and films for packaging offood, beverages, cosmetics, pharmaceuticals, and personal care productswhere a high oxygen barrier is needed. Examples of beverage bottlesinclude stretch blow molded and extrusion blow molded water bottles andcarbonated soft drinks, but the application is particularly useful inbottle applications containing juices, sport drinks, beer or any otherbeverage where oxygen detrimentally affects the flavor, fragrance,performance (e.g. due to vitamin degradation), or color of the drink.The polymer blends are also particularly useful in food trays, such asdual ovenable food trays, or cold storage food trays, both in the basecontainer and in the lidding (whether a thermoformed lid or a film),where the freshness of the food contents can decay with the ingress ofoxygen. The polymer blends also find use in the manufacture of cosmeticcontainers and containers for pharmaceuticals or medical devices.Preferably, the polyester polymer composition, including the preforms,bottles, sheets, and all the other applications are either a monolayer,or contain components (A), (B), and (C) in one layer.

Many other ingredients can be added to the compositions of the presentinvention to enhance the performance properties of the blends. Forexample, crystallization aids, impact modifiers, surface lubricants,denesting agents, stabilizers, ultraviolet light absorbing agents, metaldeactivators, colorants such as titanium dioxide and carbon black,nucleating agents such as polyethylene and polypropylene, phosphatestabilizers, fillers, and the like, can be included herein. All of theseadditives and the use thereof are well known in the art and do notrequire extensive discussions. Therefore, only a limited number will bereferred to, it being understood that any of these compounds can be usedso long as they do not hinder the present invention from accomplishingits objects.

In applications where a clear, colorless resin is desired, the slightyellow color generated during processing can be masked by addition of ablue dye. The colorant can be added to either component of the blendduring polymerization or added directly to the blend during compounding.If added during blending, the colorant can be added either in pure formor as a concentrate. The amount of a colorant depends on itsabsorptivity and the desired color for the particular application. Apreferred colorant is1-cyano-6-(4-(2-hydroxyethyl)anilino)-3-methyl-3H-dibenzo(F,I,J)-isoquinoline-2,7-dioneused in an amount of from about 2 to about 15 ppm.

Other typical additives, depending on the application, also includeimpact modifiers. Examples of typical commercially available impactmodifiers well-known in the art and useful in this invention includeethylene/propylene terpolymers, styrene based block copolymers, andvarious acrylic core/shell type impact modifiers. The impact modifiersmay be used in conventional amounts from 0.1 to 25 weight percent of theoverall composition and preferably in amounts from 0.1 to 10 weightpercent of the composition.

In many applications, not only are the packaging contents sensitive tothe ingress of oxygen, but the contents may also be affected by UVlight. Accordingly, it is also desirable to incorporate into thepolyester composition any one of the known UV absorbing compounds inamounts effective to protect the packaged contents.

EXAMPLES

The inherent viscosity values described throughout this description todescribe the pellet Ih.V. are set forth in dL/g units and is calculatedfrom an 0.50 gram sample dissolved in 10 dL of a 60/40 wt/wtphenol/tetrachloroethane at 25° C. The It.V. can be calculated from theIh.V. by the following equation:It.V.=0.5*(e ^((0.5*Ih.V.))−1)+0.75*Ih.V.

The method used to measure the terminal carboxyl group concentration isby potentiometric titration. One gram of polyamide is placed in 50milliliters of benzyl alcohol and heated until dissolved. The titrant is0.01 N potassium hydroxide in isopropanol.

Terminal amine group concentration is determined by potentiometrictitration. One gram of polyamide is dissolved in 90 mis of m-cresol at25° C. The titrant is 0.01 N perchloric acid in a ratio of 2:1isopropanol/propylene glycol. The titrant is prepared from 70%perchloric acid in water.

The hydrocarbyl end group concentration, in meq/gm or milli moles/gm, iscalculated by the number of moles of hydrocarbyl compound added to thepolyamide polymerization reaction.

Example 1

This example illustrates the effect Components (B) and (C) on the colorof a polyester composition made into a bottle.

Pellets of Voridian PET grade 9921W polyester polymer were blended withtwo versions of a polyamide of adipic acid and m-xylylene diamine, oneversion having carboxyl endgroups and the other version having aminoendgroups.

The carboxyl terminated version (CT) was prepared by the followingmethod:

In a 17 gallon stainless steel reactor vessel with a spiral agitator33.17 lbs (110.73 moles) of m-xylylene diamine was added drop wise to astirred mixture of 37.92 lbs (117.92 moles) of adipic acid and 63.6 lbsof water. The water was added to dissolve the salt and control theexotherm during its formation. A stoichiometric excess of 6.5 mole %acid was used to make about 60 lbs of a polyamide having an 0.29 Ih.V.The mixture was heated at 105° C. for 1 hour to remove the water. Thetemperature was then raised to 120° C. for 1 hour, and then to 135° C.for 0.5 hours, followed by 275° C. for 1 hour at atmospheric undernitrogen purge throughout the course of the reaction. The resulting meltwas then extruded onto dry ice and ground to pass through a 6 millimeterscreen.

The amine terminated version (AT) was prepared by the following method:

In a 17 gallon stainless steel reactor vessel with a spiral agitator,29.44 lbs (98.27 moles) of m-xylylene diamine was added drop wise to astirred mixture of 29.67 lbs (92.28 moles) of adipic acid and 53 lbs ofwater. The water was added to dissolve the salt and control the exothermduring its formation. A stoichiometric excess of 6.5mole % amine wasused to make 50 lbs of a polyamide having an Ih.V. of _(—)0.438d_dL/g.The mixture was heated at 105° C. for 1 hour to remove the water. Thetemperature was then raised to 120° C. for 1 hour, and then to 135° C.for 0.5 hours, followed by 275° C. for 1 hour at atmospheric undernitrogen purge throughout the course of the reaction. The resulting meltwas then extruded onto dry ice an ground to pass through a 6 millimeterscreen.

Both versions of the polyamides were of very low molecular weight,calculated to be about 3700 for the carboxyl terminated version andabout 7500 for the amino terminated version based upon measured endgroup concentrations using the following calculation:Mn=2*1000/(meq carboxyl/gm+meq amino/gm+meq hydrocarbyl/gm)

Where meq hydrocarbyl/gm=milli moles of hydrocarbyl/gram TABLE 1Carboxyl Amino Endgroup Endgroup Polyamide Concentration ConcentrationInherent Calculated Type (meq/g) (meq/g) Viscosity Mn Carboxyl 0.5450.0042 0.29 3700 Terminated (CT) Amino 0.0446 0.221 0.44 7500 Terminated(AT)

Pellet blends were made at 1, 3, and 5wt. % polyamide in PET 9921W aslisted in Table 2 below. The blends were made by grinding the polyamidepolymers and the polyester polymers to 3 mm. The ground polyesterpolymers were dried at 150° C. overnight, and the ground polyamidepolymers were dried at 80 C overnight. The ground polymers were thenmelt processed on a Brabender single screw extruder equipped with anEgan dispersive mixing screw at 275° C., screw speed at 100 rpm, to makepellet blends of the polyamide polymer and the polyester polymer.

Solely to initially determine the effect of the different polyamides onthe color of the blends without the addition of a cobalt oxidationcatalyst, the L*, a* and b*, were measured on the resulting pellets. TheL*, a*, b* of the pellet blends were measured directly on the pellets inreflectance mode, specular included, according to the proceduredescribed above.

The results are reported in Table 2. TABLE 2 HunterLab Pellet ColorExample # 9921W w/ L* a* b* 1-A Control 61 −1.46 0.37 1-B w/1.0% CT61.85 −2.09 2.96 1-C w/3.0% CT 64.06 −2.37 4.2 1-D w/5.0% CT 65.14 −2.424.57 1-E w/1.0% AT 60.6 −3.74 8.87 1-F w/3.0% AT 61.56 −3.55 8.17 1-Gw/5.0% AT 62.57 −3.59 8.35

As can be seen with the pellet color, a significant color improvement isobserved when using a carboxyl terminated polyamide instead of an aminoterminated polyamide. The indication of yellowness (b*) indicates adramatic effect when changing polyamide endgroups. The carboxylterminated version has 2.5-4.5 unit increase in yellowness whereas theamino terminated version has an increase of about 8.5 units. Also, thebrightness of the blends (L*) was somewhat increased to a greater degreewith increasing amounts of the carboxyl terminated polyamide comparedwith the amino terminated version.

Example 2

In this next set of experiments, the pellet blends of the polyamidepellets prepared according to the process described in Example 1 werecombined with PET 9921W polyester pellets and cobalt as an oxygenscavenging transition metal catalyst according to the process describedbelow, and then formed into a monolayer preform and stretch-blow moldedbottles. The effects of the different polyamide polymers on thetransmission rate of oxygen through the bottle wall and the inductionperiod needed to commence significant oxygen scavenging were evaluated.

Dry blends were prepared using PET 9921W, commercially available fromEastman Chemical Company, 3.0 wt. % of the low molecular weightpolyamide granules and pellets of a concentrate of cobalt catalyst inPET 9921. The catalyst concentrate was prepared by adding cobaltneodecanoate pellets to a PET 9921 melt stream on a twin screw extruder.The resulting pelletized concentrate contained about 3500 ppm Co. Themixture of PET 9921W, polyamide and catalyst concentrate (in PET 9921)was fed into a Husky Injection Molding Machine Type LX-160 havingmachine and manifold heat set points at about 280° C. and a cycle timeof about 16 seconds to form a final composition containing 3 wt. % ofthe polyamide, 100 ppm cobalt, and the remainder being PET

The total weight of pellets fed to the machine was about 30 lbs (13,620grams). The molten stream was injection molded into monolayer preformmolds suitable for forming 20 ounce bottles. The preforms were stored atambient lab conditions overnight and then blown into bottles the nextday on a Sidel SBO-2/3 stretch/blow machine. A set of comparativeexamples (control) were made which contained neither cobalt norpolyamide polymer.

The bottles were fitted the day following blow molding for oxygenpackage transmission testing using the procedure described above formeasuring oxygen transmission rates on the Oxtran. Triplicate bottlesfrom each type of blend were used for the testing and package oxygentransmission was measured on a semi-random basis for the next severalmonths. Table 3 sets forth the OTR results for Control bottles made withthe base polyester polymer without polyamide, polyester polymer madewith 3 wt. % amine terminated polyamide containing 100 ppm Co, andpolyester polymer made with 3wt. % carboxylic acid terminated polyamidecontaining 100 ppm Co. TABLE 3 Oxygen transmission rates of 25 gram, 20oz bottles PET 9921W Control (Without Polyamide With 3 wt. % AT With 3wt. % CA and without cobalt) @ 100 ppm Co @ 100 ppm Co Days OTR OTR OTRSince (cc (cc (cc Blow STP/ Bottle STP/ Bottle STP/ Bottle Molding day)Sample day) Sample day) Sample 4 0.0571 2 0.0399 3 0.0397 3 4 0.0585 10.0401 1 0.0374 2 4 0.0569 3 0.0391 3 0.0390 1 32 0.0549 3 0.0372 20.0006 2 36 0.0498 2 0.0360 1 0.0016 3 36 — — 0.0371 3 — — 41 0.0543 1 —— 0.0017 1 53 0.0505 1 — — 0.0014 1 64 0.0508 3 0.0274 1 0.0003 2 76 — —0.0202 2 0.0009 3 81 — — 0.0159 3 — — 97 — — — — 0.0007 1 103 — — 0.02013 — — 109 — — 0.0168 3 — — 113 — — — — 0.0008 3 120 — — — — 0.0006 2 123— — 0.0137 3 — — 123 — — 0.0247 1 — — 137 — — 0.0212 2 — — 158 — — — —0.0007 3 158 — — — — 0.0007 1 165 — — 0.0236 1 — — 187 — — 0.0298 1 — —268 — — 0.0022 3 0.0009 2 353 — — 0.0030 1 — — 358 — — 0.0057 3 — —

The polyester composition containing the carboxyl terminated polyamideexhibited an induction period, defined as an oxygen transmission ratefalling below 0.020 cc STP/day, of significantly less than 32 days. Bycontrast, the polyester composition containing the amino terminatedpolyamide exhibited an induction period of greater than 75 days. Thus,the induction period for polyester compositions containing the carboxylterminated polyamide was about ¼ that of a polyester compositioncontaining an amino terminated polyamide. Moreover, the polyesterpolymer composition containing the carboxyl terminated polyamide had anoxygen transmission rate of less than 0.010 cc STP/day for at least 230consecutive days, and even was less than 0.005 cc STP/day for at least230 consecutive days. By contrast, the polyester composition containingthe amino terminated polyamide only attained an, oxygen transmissionrate of less than 0.010 cc after 187 days.

Example 3

This example illustrates the effect of only 1 wt. % predominately acidterminated polyamide and 100 ppm Co on the oxygen scavenging capabilityof the composition relative to a composition containing a polyamidepredominately amine terminated. Samples were prepared and treated asdescribed in Example 2, except the polyamide level was adjusted to yield1 wt. % in the final blend. The oxygen transmission rates determined forthese bottles are presented in Table 4. TABLE 4 Oxygen transmissionrates of 25 gram, 20 oz bottles PET 9921W Control With 1 wt. % AT With 1wt. % CA (Without Polyamide) @ 100 ppm Co @ 100 ppm Co Days OTR OTR OTRSince (cc (cc (cc Blow STP/ Bottle STP/ Bottle STP/ Bottle Molding day)Sample day) Sample day) Sample 4 0.0571 2 0.0473 1 0.0500 1 4 0.0585 10.0500 3 0.0482 2 4 0.0569 3 0.0507 2 0.0511 3 32 0.0549 3 0.0488 1 — —36 0.0498 2 0.0464 3 0.0491 2 36 — — — — 0.0446 1 41 0.0543 1 0.0492 20.0417 3 53 0.0505 1 0.0478 2 — — 64 0.0508 3 0.0465 1 0.0491 3 76 — —0.0435 3 0.0434 1 81 — — — — 0.0445 2 95 — — 0.0418 2 — — 103 — — 0.04061 0.0427 2 109 — — 0.0396 1 0.0427 2 113 — — — — 0.0381 3 113 — — — —0.0419 1 123 — — 0.0432 2 0.0400 2 123 — — — — 0.0424 1 152 — — 0.04263− 0.0391 1 158 — — 0.0410 1 — — 165 — — 0.0436 2 0.0322 3 268 — — — —0.0317 2 374 — — 0.0329 2 0.0250 3 377 — — — — 0.0299 3

The results indicate that the oxygen transmission rate of thecomposition of the invention is slightly reduced after about 120 daysrelative to a composition containing amine terminated polyamides and onecan begin to see some improvement even at even at low levels ofpolyamide and cobalt. To obtain the best results, however, largerquantities or polyamide, transition metal, or both are preferred.

Example 4

This example illustrates the effect of increasing the concentration ofpredominately acid terminated polyamide to 5 wt. % on oxygentransmission while retaining the same level of Co at 100 ppm, andfurther illustrates the effect relative to a composition containing apredominately amine terminated polyamide. Samples were prepared andtreated as described in Example 2, except the polyamide level wasincreased to yield 5% in the final blend. The oxygen transmission ratesdetermined for these bottles are presented in Table 5. TABLE 5 Oxygentransmission rates of 25 gram, 20 oz bottles PET 9921W Control With 5wt. % AT With 5 wt. % CA (Without Polyamide) @ 100 ppm Co @ 100 ppm CoDays OTR OTR OTR Since (cc (cc (cc Blow STP/ Bottle STP/ Bottle STP/Bottle Molding day) Sample day) Sample day) Sample 4 0.0571 2 0.0313 20.0143 2 4 0.0585 1 0.0315 1 0.0141 1 4 0.0569 3 0.0324 3 0.0230 3 320.0549 3 0.0303 2 0.0006 3 36 0.0498 2 0.0223 1 0.0005 2 36 — — 0.0249 3— — 41 0.0543 1 — — — — 46 — — — — 0.0010 2 53 0.0505 1 — — — — 640.0508 3 0.0146 1 0.0006 3 76 — — 0.0088 2 0.0009 1 81 — — 0.0094 3 0.095 — — — — 0.0004 2 103 — — 0.0142 1 — — 113 — — 0.0113 1 — — 120 — —0.0181 2 0.0005 3 120 — — 0.0184 3 — — 123 — — 0.0165 2 — — 137 — —0.0151 3 — — 137 — — 0.0104 1 — — 152 — — — — 0.0003 2 152 — — — —0.0011 1 165 — — 0.0147 2 — — 165 — — 0.0133 1 — — 187 — — 0.0112 3 — —268 — — 0.0039 3 — — 353 — — Error 2 — — 358 — — 0.0020 3 — —

The results indicate that the induction time using carboxyl terminatedpolyamide is significantly less than when using the amine terminatedpolyamide. As early as day 4, the oxygen transmission rate for carboxylterminated polyamide compositions was about ¼ that of the control. Byday 32, the oxygen transmission rate had plummeted to 0.0006 cc STP/day,which was about 1/50 the transmission rate of the amine terminatedpolyamide composition. Even using the oxygen transmission rate at day 4,where the bottles with carboxyl terminated polyamide already exhibitevidence of oxygen scavenging, as a starting point, it took less than 32days for oxygen transmission rate of the composition containing thecarboxyl terminated polyamide to be reduced an additional 50%, comparedto about 64 days for the amine terminated polyamide composition.

Once oxygen scavenging was activated, the oxygen transmission rate forthe composition containing the carboxyl terminated polyamide remained ata very low level—less than 0.005 cc STP/day—over a period of at least120 days. While the oxygen scavenging activity of the compositioncontaining 5 wt. % CT was excellent, it is believed that using about nomore than 3.5 wt. % of the carboxyl terminated polyamide is optimalbecause the similar performance can be achieved at low levels of 3 wt.%, while saving on material costs. (Compare Example 2)

Example 5

This example illustrates the effect of using a predominately acidterminated polyamide on b* color relative to the use of the same amountof a predominately amine terminated polyamide. In each case, thepolyester composition made with a polyamide polymer and contained about100 ppm Co metal, using the procedures and ingredients set forth inExamples 1 and 2.The b* was measured on the preform at the center of thesidewall having a thickness of about 144 mils according to the testmethod described above.

The results are provided below in Table 6. AT means amine terminatedpolyamide, and CT means carboxylic acid terminated polyamide. TABLE 6 20ounce preform color Reference Description b* color A Control 4.4 B 1.0wt. % AT 14.82 C 3.0 wt. % AT 4.13 D 4.8 wt. % AT −6.12 E 1.0 wt. % CT−0.83 F 3.0 wt. % CT −5.62 G 5.0 wt. % CT −9.8

The b* color of compositions containing the carboxylic acid terminatedpolyamide and cobalt was much lower than equivalent compositionscontaining the amine terminated polyamide. With these compositions, blueor neutral bottles can be made with lower amounts of bluing toners sincethe b* color values were much less than the compositions containing theamine terminated polyamide.

Many variations will suggest themselves to those skilled in this art inlight of the above detailed description. All such obvious modificationsare within the full intended scope of the appended claims.

1. A polyester polymer composition comprising (A) a polyester polymercomprising: (i) a polycarboxylic acid component comprising at least 60mole % of the residues of terephthalic acid, derivates of terephthalicacid, naphthalene-2,6-dicarboxylic acid, derivatives ofnaphthalene-2,6-dicarboxylic acid, or mixtures thereof, and (ii) apolyhydroxyl component comprising at least 30 mole % of the residues ofC₂-C₄ aliphatic saturated diols, based on 100 mole percent of thepolycarboxylic acid compound residues and 100 mole percent polyhydroxylcompound residues in the polyester polymer, respectively; (B) apolyamide polymer in an amount ranging from 0.10% wt. % to 10.0 wt. %,based on the weight of (A) and (B), having a C:A terminal groupconcentration ratio of 2:1 or more and a C+A terminal groupconcentration of at least 0.17 meq/g of polyamide polymer, wherein Crepresents a cumulative total of a terminal carboxyl group concentrationand a terminal hydrocarbyl group concentration expressed in meq/g ofpolyamide, and A represents a terminal amine group concentrationexpressed in meq/g of polyamide; and (C) an oxygen scavenging transitionmetal catalyst.
 2. A monolayer preform or a beverage bottle comprisingthe composition of claim
 1. 3. The composition of claim 1, wherein thepolyester polymer comprises a blend of: (i) a polycarboxylic acidcomponent comprising at least 85 mole % of the residues of terephthalicacid or its derivates or mixtures thereof; and (ii) a polyhydroxylcomponent comprising at least 85 mole % of the residues of ethyleneglycol based on 100 mole percent of the polycarboxylic acid compoundresidues and 100 mole percent polyhydroxyl compound residues in thepolyester polymer.
 4. The composition of claim 3, wherein the C:A ratiois at least 50:1.
 5. The composition of claim 4, wherein the numberaverage molecular weight of the polyamide is 11,500 or less, and the C:Aratio is at least 100:1.
 6. The composition of claim 5, wherein thepolyamide comprises a partially aromatic polyamide having a numberaverage molecular weight of 7,500 or less.
 7. The composition of claim1, wherein the transition metal comprises cobalt in an amount of atleast 50 ppm.
 8. The composition of claim 1, wherein said composition isblow molded into a bottle, and for a continuous period of 50 daysmeasured at any time within a period after the manufacture of a blowmolded bottle and before 100 days after its manufacture, the oxygentransmission rate of oxygen through the bottle does not exceed 0.02 ccSTP/day.
 9. The composition of claim 8, wherein the oxygen transmissionrate does not exceed 0.01 cc STP/day.
 10. The composition of claim 9,wherein the oxygen transmission rate does not exceed 0.005 cc STP/day.11. The composition of any one of claim 8-10, wherein the 50 daycontinuous period begins within 15 days after making the blow moldedbottle.
 12. The composition of claim 8, wherein the composition used tomake said bottle in a form other than a bottle, and/or the bottle madefrom the composition, has an a* of +3.0 or less and a b* of +3.0 or lessas measured on a preform, respectively, wherein the composition containsfrom 50 ppm cobalt to 250 pm cobalt and said polyamide in an amount from1.0 to 5.0 wt. % based on the weight of the composition.
 13. Thecomposition of claim 1, wherein the C:A ratio is at least 100:1.
 14. Thecomposition according to claim 1 wherein said polyamide is obtained froma reactant containing an active methylene hydrogen atom.
 15. Thecomposition according to claim 1, wherein said polyamide is obtainedfrom a reactant containing a benzylic hydrogen atom.
 16. The compositionof claim 15, wherein the polyamide comprises a poly(m-xylyleneadipamide) modified or unmodified polyamide polymer.
 17. The compositionof claim 1, wherein said polyamide comprises the reaction product of: a.xylylene diamine; and b. adipic acid or isophthalic acid or terephthalicacid or octanoic acid or heptanoic acid; and c. a hydrocarbyl cappingagent.
 18. The composition of claim 1, wherein said polyamide isobtained from a reactant containing an allylic hydrogen atom.
 19. Thecomposition of claim 18, wherein the reactant comprises apoly(1,4-butadiene) moiety or a poly(1,2-butadiene) moiety.
 20. Thecomposition of claim 1, wherein the polyamide is obtained from areactant containing an oxyalkyelne hydrogen atom.
 21. The composition ofclaim 20, wherein the reactant comprises a polyoxyalkylene polyethermoiety.
 22. The composition of claim 21, wherein the reactant comprisesa polyether moiety comprising oxypropylene groups, oxybutylene groups,tetramethylene groups, or a mixture thereof.
 23. A blow molded polyesterbottle having an oxygen transmission rate of 0.02 cc STP/day or less fora continuous period of 40 days between the time the bottle ismanufactured and 100 days thereafter, wherein the bottle comprises anoxygen scavenging transition metal in an amount of 400 ppm or less, anda polyamide having a C:A ratio of 2:1 or more and a total C+A terminalgroup concentration of at least 0.17 meq/g.
 24. The bottle of claim 23,wherein the oxygen transmission rate is 0.010 cc STP/day or less. 25.The bottle of claim 24, wherein the continuous period of 40 days isbetween the time the bottle is manufactured and 60 days thereafter. 26.The bottle of claim 23, wherein the transition metal is cobalt in anamount of at least 50 ppm.
 27. The bottle of claim 18, wherein saidoxygen transmission rate is maintained for a period of 100 days.
 28. Thebottle of claim 18, wherein said polyamide has a C:A ratio of at least100:1.
 29. A polyester polymer composition comprising: (A) a polyesterpolymer comprising: (i) a polycarboxylic acid component comprising atleast 60 mole % of the residues of terephthalic acid, derivates ofterephthalic acid, naphthalene-2,6-dicarboxylic acid, derivatives ofnaphthalene-2,6-dicarboxylic acid, or mixtures thereof, and (ii) apolyhydroxyl compound component comprising at least 30 mole % of theresidues of C₂-C₄ aliphatic saturated diols, based on 100 mole percentof the polycarboxylic acid residues and 100 mole percent polyhydroxylcompound residues in the polyester polymer; and (B) a polyamide polymerin an amount ranging from 10% wt. % to 50.0 wt. %, based on the weightof (A) and (B), having a C:A terminal group concentration ratio of 2:1or more and a C+A terminal group concentration of at least 0.17 meq/g ofpolyamide polymer, wherein C represents a cumulative total of a terminalcarboxyl group concentration and a terminal hydrocarbyl groupconcentration expressed in meq/g of polyamide, and A represents aterminal amine group concentration expressed in meq/g of polyamide. 30.The composition of claim 24, wherein the polyester polymer comprises:(i) a polycarboxylic acid component comprising at least 85 mole % of theresidues of terephthalic acid or its derivates or mixtures thereof; and(ii) a polyhydroxyl compound component comprising at least 85 mole % ofthe residues of ethylene glycol based on 100 mole percent of thepolycarboxylic acid residues and 100 mole percent polyhydroxyl compoundresidues in the polyester polymer.
 31. The composition of claim 24,wherein the C:A ratio is at least 50:1.
 32. The composition of claim 24,comprising a monolayer preform or a monolayer beverage bottle comprisingsaid composition.
 33. The composition of claim 24, wherein the numberaverage molecular weight of the polyamide is 10,000 or less.
 34. Thecomposition of claim 28, wherein the polyamide comprises a partiallyaromatic polyamide having a number average molecular weight of 7,500 orless.
 35. The composition of claim 24, wherein the transition metalcomprises cobalt in an amount of at least 50 ppm.
 36. The composition ofclaim 30, wherein said composition is combined with additional polyesterpolymer, followed by blow molding into a bottle, and for a continuousperiod of 50 days measured at any time within a period after themanufacture of a blow molded bottle and before 100 days after itsmanufacture, the oxygen transmission rate of oxygen through the bottledoes not exceed 0.020 cc STP/day.
 37. The composition of claim 31,wherein the oxygen transmission rate does not exceed 0.010 cc STP/day.38. The composition of claim 32, wherein the oxygen transmission ratedoes not exceed 0.005 cc STP/day.
 39. The composition of claim 32,wherein the composition used to make said bottle in a form other than abottle, and/or the bottle made from the composition, has a b* of +3.0 orless as measured on a preform, respectively, wherein the compositioncontains from 50 ppm cobalt to 250 pm cobalt and said polyamide in anamount from 1.0 to 5.0 wt. % based on the weight of the composition. 40.The composition of claim 34, wherein the C:A ratio is 100:1 or more. 41.The composition of any one of claims 31-33, wherein the 50 daycontinuous period begins within 35 days after making the blow moldedbottle.
 42. The composition according to claim 24 wherein said polyamidecomprises a compound having benzylic hydrogen atoms.
 43. The compositionaccording to claim 24, wherein said polyamide contains a xylylenemoiety.
 44. The composition according to claim 24, wherein the polyamidecomprises poly (m-xylylene adipamide).
 45. A polyester polymercomposition comprising: (A) a polyester polymer comprising: (i) apolycarboxylic acid component comprising at least 60 mole % of theresidues of terephthalic acid, derivates of terephthalic acid, ormixtures thereof, and (ii) a polyhydroxyl compound component comprisingat least 30 mole % of the residues of ethylene glycol, based on 100 molepercent of the polycarboxylic acid residues and 100 mole percentpolyhydroxyl compound residues in the polyester polymer, respectively;and (B) a polyamide polymer in an amount ranging from 0.10% wt. % to50.0 wt. %, based on the weight of (A) and (B), having a C:A terminalgroup concentration ratio of 100:1 or more, wherein C represents thecumulative total of a terminal carboxyl group concentration and terminalhydrocarbyl group concentration, and A represents a terminal amine groupconcentration; and (C) cobalt in an amount of at least 50 ppm based onthe weight of the polyester composition.
 46. The composition of claim40, wherein the composition and/or the bottle made from the compositionhas a b* of +5.0 or less and a b* of +5.0 or less as measured on apreform respectively.
 47. The composition of claim 40, wherein thepolyamide has a C:A ratio of at least 200:1.
 48. The composition ofclaim 40, wherein the polyamide has a number average molecular weight ofless than 11,500.
 49. The composition of claim 40, wherein saidcomposition is blow molded into a bottle, and for a continuous period of50 days measured at any time within a period after the manufacture of ablow molded bottle and before 100 days after its manufacture, the oxygentransmission rate of oxygen through the bottle does not exceed 0.020 ccSTP/day.
 50. The composition of claim 44, wherein the oxygentransmission rate does not exceed 0.010 cc STP/day.
 51. The compositionof claim 45, wherein the oxygen transmission rate does not exceed 0.005cc STP/day.
 52. The composition of any one of claims 44-46, wherein the50 day continuous period begins within 35 days after making the blowmolded bottle.
 53. A blow molded polyester monolayer bottle having anoxygen transmission rate below 0.01 cc STP/day for a continuous periodof at least 180 days commencing no later than 50 days from themanufacture of the bottle, wherein the bottle comprises a polyesterpolymer comprising: (i) a polycarboxylic acid component comprising atleast 60 mole % of the residues of terephthalic acid, derivates ofterephthalic acid, naphthalene-2,6-dicarboxylic acid, derivatives ofnaphthalene-2,6-dicarboxylic acid, or mixtures thereof, and (ii) apolyhydroxyl component comprising at least 30 mole % of the residues ofC₂-C₄ aliphatic saturated diols, based on 100 mole percent of thepolycarboxylic acid compound residues and 100 mole percent polyhydroxylcompoundresidues in the polyester polymer, respectively.
 54. The blowmolded bottle of claim 53, commencing not later than 35 days frommanufacture of the bottle.
 55. The blow molded bottle of claim 54,continuing for a period of at least 180 days.
 56. The blow molded bottleof claim 53, wherein the bottle comprises an oxygen scavengingtransition metal in an amount of 400 ppm or less, and a polyamide havinga C:A ratio of 2:1 or more and a total C+A terminal group concentrationof at least 0.17 meq/g.
 57. The blow molded bottle of claim 53, whereinthe polyester polymer comprises: (i) a polycarboxylic acid componentcomprising at least 85 mole % of the residues of terephthalic acid,derivates of terephthalic acid, naphthalene-2,6-dicarboxylic acid,derivatives of naphthalene-2,6-dicarboxylic acid, or mixtures thereof,and (ii) a polyhydroxyl component comprising at least 85 mole % of theresidues of C₂-C₄ aliphatic saturated diols, based on 100 mole percentof the polycarboxylic acid compound residues and 100 mole percentpolyhydroxyl compoundresidues in the polyester polymer, respectively.